Roof and waterproofing membranes and linings have long been used to protect buildings, to contain water in ponds and decorative water features, to prevent leaching of contaminants from landfills, and for other purposes. While these membranes have utility, leakage through the membranes is an ongoing problem. The efforts to contain and locate leakage have resulted in the rise of specialized consultants, air and vacuum testable membranes, and, in recent history, electrical testing methods that not only determine if a leak is present in a membrane system, but where the leak is located.
Because of recurring problems with leakage, designers are starting to plan roofing and waterproofing assemblies which have two or more distinct layers and which comprise the same or different type of membrane for each layer with each layer separated by construction materials, such as insulation, which creates a space between the membranes. These designs are used over critical spaces where leakage of any sort cannot be tolerated, such as hospitals, laboratories, libraries and book depositories, data centers and museums, to name a few. What used to be considered a vapor barrier applied to the roof deck to prevent vapor incursion into the roofing envelope from the space below now often serves double duty and is considered to be a secondary protection membrane capable of stopping water that encroaches into the roofing envelope due to leakage in the primary, uppermost membrane. Put in another way, the top layer of membrane is the primary waterproofing layer which is responsible for keeping the entire roofing or waterproofing envelope and the space under the envelope protected from moisture. The second and, if designed, third or more lower layers, act as back-up protection for leakage from the primary membrane in that, if the primary waterproofing layer does leak, the water will theoretically be stopped by the secondary or even subsequently lower waterproofing layer or layers.
This system of multiple membranes is well known in the environmental containment industry, which uses at least two sets of liners, the first to act as the primary containment and the others to act as the secondary or tertiary containment and leak detection layer. These multiple membrane systems are in common use in landfills, lagoons, and other structures which contain solids, or water and waste that can generate an unwanted flow of leachate or other waterborne contaminants into the surrounding land or ground water.
It is also known that the multiple membrane systems can be fitted with automatic leak detection systems, usually located between the two liners, if a dual system, or at the bottom liner. Underground and above ground storage tanks can have the same features. These leak detection systems operate either by directly sensing liquid which has come into the secondary containment space from a breach in the primary containment, or by charging the top surface of the primary containment, which charge is detected by a sensor array under the primary containment and above the secondary or tertiary liner. Systems, such as those sold under the trademark Geologger, owned by Progeo GmbH, are designed to detect leaks in this fashion.
In civil structures, the secondary liner does not have leak detection that determines its own integrity and normally has drainage structures, pipes and channels to evacuate any accumulated leakage from the primary liner that impacts the secondary liner safely to the outside of the lined facility. The ability of dual lined civil structures to drain both the primary and secondary liners is accomplished by sloping the soils upon which the liners are placed. There are normally no occupied spaces underneath these civil structures. Further, it is recognized by the engineering community and by the governments in many countries that civil liners may leak a small quantity because of the stresses and loads applied to these membranes. Civil membranes are often very difficult to reach once in service without removing massive amounts of overburden, as is the case in landfills etc., or draining large sewage or chemical retention ponds in order to get at areas that cause small amounts of leakage. Thus the criterion, 20 gallons per acre per day per foot of water head has been developed by the government in conjunction with the engineering community as an acceptable level of leakage for civil membranes.
This is not the case with the roofs, decks and foundations of buildings. These types of structures often rely on level decks and vertical walls upon which they construct the roofing and waterproofing. Tapered insulation often provides the primary slope for roof drainage, and there is almost always occupied space under the roofing and waterproofing membranes. Further, it is recognized, and is the subject of numerous cases in the courts and in arbitrations, that these membranes are not supposed to leak at all and are expected to fulfill this function perfectly.
Roofing and waterproofing in buildings can be tested in the same way as civil membranes, and other Progeo Smartex systems and systems designed by others accommodate this feature. However, with the advent of multiple layer roofs in which the roofing or waterproofing membranes are separated from one another by insulation or other building materials, it is difficult to test and report on all the layers of membranes using one integrated real-time automated system and to determine exactly the time and source of any leakage at any level. To complicate matters, water that incurs at the edges of the primary waterproofing or roofing membrane or at the secondary roofing or waterproofing membranes is not automatically and/or timely detected on all levels by the design of any currently existing automatic leak detection system. Thus, water incursion into the roofing or waterproofing envelope from exterior structures impinging on the roofing membrane or envelope such as window walls, curtain walls, vents, mechanical units, curbs, parapets and the like normally goes undetected until such leakage shows up in the building. By that time, some portion, or all of the area of the secondary or tertiary backup membranes is saturated. This lack of detection, then, leads to roofs in which the insulation in the roofing envelope becomes saturated with water incurring from the above described edges of the roofing system. The leakage remains completely undetected because of the lower, secondary roofing or waterproofing membrane or because the vapor barrier is holding the water back.
Leakage is only detected when water sitting on the secondary membrane overtops the curb, penetrations through the roof deck, top of the window wall or curtain wall, or leaks through a damaged portion or a faulty seam in the secondary membrane, or the like. Further, it is never known for certain where the water which is now on the secondary membrane has come from. It could have come from a leak in the primary roofing membrane, from a penetration through the roof as described above, or from walls directly adjacent to the roof, all of which contain flashing designed to keep water out of the roofing envelope. A further complication is that oftentimes this leakage falls directly from a penetration or impinging structure without ever affecting the roofing envelope, but is blamed on the roofing envelope as water is “coming from the roof”
This current invention proposes to solve the above-mentioned problems by providing a combination of known methods for automatically detecting leakage in the primary roofing membrane, detecting leakage in the secondary roofing membrane, and a new method to monitor all of the edge conditions around the secondary roofing membrane regarding any water incursion into the system.